In turbochargers of this kind, a phenomenon is occurring during operation that is called “blow-by”. This means that with an elevated exhaust gas pressure, i.e. with elevated numbers of revolution, the tendency can be observed that the exhaust gas flows from the turbine housing through unavoidable leakages into the region of the bearings, often accommodated in a separate bearing housing intermediate between the turbine housing and the compressor housing. Likewise, with elevated numbers of revolution and elevated charging pressure, air sucked into the compressor housing has the tendency to flow over a sealing, e.g. a piston ring, at the side of the compressor to the region of the bearings or the intermediate bearing housing.
Furthermore, with low charging pressure and a high number of revolutions, there exists the possibility that an oily mixture of air and exhaust gas from the region of the bearings flows in the direction of the compressor housing so that the emissive behavior is worsened.